HDP-CVD multistep gapfill process

Abstract

A gapfill process is provided using cycling of HDP-CVD deposition, etching, and deposition step. The fluent gas during the first deposition step includes an inert gas such as He, but includes H 2 during the remainder deposition step. The higher average molecular weight of the fluent gas during the first deposition step provides some cusping over structures that define the gap to protect them during the etching step. The lower average molecular weight of the fluent gas during the remainder deposition step has reduced sputtering characteristics and is effective at filling the remainder of the gap.

What is claimed is: 
     
       1. A method for depositing a film to fill a gap in a surface of a substrate, the method comprising:
 depositing a first portion of the film in the gap using a first gaseous mixture in a high-density-plasma chemical-vapor-deposition (HDP-CVD) process, the first gaseous mixture consisting of a first process gas and a first fluent gas, the first process gas having chemical elements incorporated into the film and the first fluent gas not having chemical elements incorporated into the film, wherein the first process gas comprises a silicon-containing gas and an oxygen-containing gas; 
 thereafter, etching the film with a fluorine-containing gas; and 
 thereafter, depositing a remainder of the film in the gap using a remainder gaseous mixture in an HDP-CVD process, the remainder gaseous mixture consisting of a second process gas and a second fluent gas, the second process gas having chemical elements incorporated into the film and the second fluent gas not having chemical elements incorporated into the film, wherein the second process gas comprises a silicon-containing gas and an oxygen-containing gas, 
 wherein the second fluent gas has a lower average molecular weight than the first fluent gas. 
 
     
     
       2. The method recited in  claim 1  wherein the first fluent gas comprises an inert gas and the second fluent gas comprises H 2 . 
     
     
       3. The method recited in  claim 2  wherein the first fluent gas comprises He. 
     
     
       4. The method recited in  claim 3  wherein the first fluent gas further comprises H 2 . 
     
     
       5. The method recited in  claim 2  wherein the first fluent gas comprises He and Ar. 
     
     
       6. The method recited in  claim 2  wherein the first fluent gas comprises a mixture of Ar and He. 
     
     
       7. The method recited in  claim 6  wherein the mixture of Ar and He comprises greater than 95 wt. % He. 
     
     
       8. The method recited in  claim 6  wherein the mixture of Ar and He comprises greater than 99 wt. % He. 
     
     
       9. The method recited in  claim 1  wherein etching the film comprises etching the film with an etching gaseous mixture comprising the fluorine-containing gas, an oxygen-containing gas, He, and Ar. 
     
     
       10. The method recited in  claim 1  wherein etching the film comprises applying an electrical bias to the substrate. 
     
     
       11. The method recited in  claim 1  wherein depositing the first portion of the film comprises depositing the first portion of the film with a deposition/sputter ratio within the range of 10–30, wherein the deposition/sputter ratio is defined as a ratio of a sum of a net deposition rate and a blanket sputtering rate to the blanket sputtering rate. 
     
     
       12. The method recited in  claim 1  wherein depositing the remainder of the film comprises depositing the remainder of the film with a deposition/sputter ratio within the range of 4–10, wherein the deposition/sputter ratio is defined as a ratio of a sum of a net deposition rate and a blanket sputtering rate to the blanket sputtering rate. 
     
     
       13. The method recited in  claim 1  wherein depositing the first portion of the film comprises filling between 35% and 85% of a depth of the gap. 
     
     
       14. The method recited in  claim 1  wherein etching the film comprises removing between 5% and 15% of a thickness of the first portion of the film. 
     
     
       15. The method recited in  claim 1  further comprising passivating the film after etching the film and before depositing the remainder of the film. 
     
     
       16. The method recited in  claim 15  wherein passivating the film comprises exposing the film to an oxygen atmosphere. 
     
     
       17. The method recited in  claim 1  further comprising depositing a second portion of the film in the gap using a second gaseous mixture in an HDP-CVD process, the second gaseous mixture comprising a silicon-containing gas, an oxygen-containing gas, and H 2 , wherein depositing the second portion is performed after depositing the first portion and before etching the film. 
     
     
       18. The method recited in  claim 17  wherein depositing the second portion of the film comprises depositing the second portion of the film with a second deposition/sputter ratio within the range of 5–15, wherein the second deposition/sputter ratio is defined as a ratio of a sum of a second net deposition rate and a second blanket sputtering rate to the second blanket sputtering rate. 
     
     
       19. The method recited in  claim 18  wherein depositing the first portion of the film comprises depositing the first portion of the film with a first deposition/sputter ratio within the range of 10–30, wherein the first deposition/sputter ratio is defined as a ratio of a sum of a first net deposition rate and a first blanket sputtering rate to the first blanket sputtering rate. 
     
     
       20. The method recited in  claim 17  wherein depositing the first portion of the film comprises filling between 40% and 65% of a depth of the gap. 
     
     
       21. The method recited in  claim 20  wherein depositing the second portion of the film comprises filling an additional 20%–45% of the depth of the gap. 
     
     
       22. The method recited in  claim 17  etching the film comprises removing between 5% and 15% of a combined thickness of the first and second portions of the film. 
     
     
       23. A computer-readable storage medium having a computer-readable program embodied therein for directing operation of a substrate processing system including a process chamber; a plasma generation system; a substrate holder; and a gas delivery system configured to introduce gases into the process chamber, the computer-readable program including instructions for operating the substrate processing system to deposit a film to fill a gap in a surface of a substrate disposed in the process chamber in accordance with the following:
 depositing a first portion of the film in the gap using a first gaseous mixture in a high-density-plasma chemical-vapor-deposition (HDP-CVD) process, the first gaseous mixture consisting of a first process gas and a first fluent gas, the first process gas having chemical elements incorporated into the film and the first fluent gas not having chemical elements incorporated into the film, wherein the first process gas comprises a silicon-containing gas and an oxygen-containing gas; 
 thereafter, etching the film with a fluorine-containing gas; and 
 thereafter, depositing a remainder of the film in the gap using a remainder gaseous mixture in an HDP-CVD process, the remainder gaseous mixture consisting of a second process gas and a second fluent gas, the second process gas having chemical elements incorporated into the film and the second fluent gas not having chemical elements incorporated into the film, wherein the second process gas comprises a silicon-containing gas and an oxygen-containing gas, 
 wherein the second fluent gas has a lower average molecular weight than the first fluent gas. 
 
     
     
       24. The computer-readable storage medium recited in  claim 23  wherein the first fluent gas comprises an inert gas and the second fluent gas comprises H 2 . 
     
     
       25. The computer-readable storage medium recited in  claim 24  wherein the first fluent gas comprises He. 
     
     
       26. The computer-readable storage medium recited in  claim 25  wherein the first fluent gas further comprises H 2 . 
     
     
       27. The computer-readable storage medium recited in  claim 24  wherein the first fluent gas comprises a mixture of He and Ar. 
     
     
       28. The computer-readable storage medium recited in  claim 23  wherein etching the film comprises applying an electrical bias to the substrate. 
     
     
       29. The computer-readable storage medium recited in  claim 23  wherein the computer-readable program further includes instructions for depositing a second portion of the film in the gap using a second gaseous mixture in an HDP-CVD process, the second gaseous mixture comprising a silicon-containing gas, an oxygen-containing gas, and H 2 , wherein depositing the second portion is performed after depositing the first portion and before etching the film. 
     
     
       30. A substrate processing system comprising:
 a housing defining a process chamber; 
 a high-density plasma generating system operatively coupled to the process chamber; 
 a substrate holder configured to hold a substrate during substrate processing; 
 a gas-delivery system configured to introduce gases into the process chamber; 
 a pressure-control system for maintaining a selected pressure within the process chamber; 
 a controller for controlling the high-density plasma generating system, the gas-delivery system, and the pressure-control system; and 
 a memory coupled to the controller, the memory comprising a computer-readable medium having a computer-readable program embodied therein for directing operation of the substrate processing system to fill a gap in a surface of the substrate, the computer-readable program including:
 instructions to deposit a first portion of the film in the gap using a first gaseous mixture in a high-density-plasma chemical-vapor-deposition (HDP-CVD) process, the first gaseous mixture consisting of a first process gas and a first fluent gas, the first process gas having chemical elements incorporated into the film and the first fluent gas not having chemical elements incorporated into the film, wherein the first process gas comprises a silicon-containing gas and an oxygen-containing gas; 
 instructions thereafter to etch the film with a fluorine-containing gas; and 
 instructions thereafter to deposit a remainder of the film in the gap using a remainder gaseous mixture in an HDP-CVD process, the remainder gaseous mixture consisting of a second process gas and a second fluent gas, the second process gas having chemical elements incorporated into the film and the second fluent gas not having chemical elements incorporated into the film, wherein the second process gas comprises a silicon-containing gas and an oxygen-containing gas, 
 
 wherein the second fluent gas has a lower average molecular weight than the first fluent gas. 
 
     
     
       31. The substrate processing system recited in  claim 30  wherein the second fluent gas comprises H 2 . 
     
     
       32. The substrate processing system recited in  claim 31  wherein the first fluent gas comprises He. 
     
     
       33. The substrate processing system recited in  claim 32  wherein the first fluent gas further comprises H 2 . 
     
     
       34. The substrate processing system recited in  claim 31  wherein the first fluent gas comprises a mixture of Ar and He. 
     
     
       35. The substrate processing system recited in  claim 30  wherein the instructions for etching the film comprise instructions for applying an electrical bias to the substrate. 
     
     
       36. The substrate processing system recited in  claim 30  wherein the computer-readable program further includes instructions for depositing a second portion of the film in the gap using a second gaseous mixture in an HDP-CVD process, the second gaseous mixture comprising a silicon-containing gas, an oxygen-containing gas, and H 2 , wherein the second portion is deposited after the first portion and before the etching.